1. Field of the Invention
In recent years, the clock frequency of a CPU tends to be more and more increased in an attempt to manufacture an electronic computer capable of achieving an arithmetic processing more rapidly. Nowadays, a CPU having a clock frequency of 1 GHz order has come to be put on the market.
2. Description of the Related Art
In general, the signal speed between elements outside an electric element is increased with increases in the clock frequency inside the electric element. Therefore, a portion in which a high frequency current flows is present in the electric wiring made of copper on the printed circuit board included in an electronic computer. As a result, a malfunction is brought about by the noise generation. Also, an electromagnetic wave is generated so as to give an adverse effect to the surrounding environment.
In order to overcome the problems described above, an optical wiring utilizing an optical fiber or an optical waveguide is substituted for a part of the electric wiring made of copper on the printed circuit board so as to utilize the optical signal in place of the electric signal. The optical signal is utilized because, in the case of the optical signal, it is possible to suppress the generation of the noise and the electromagnetic wave.
However, an electric wiring is formed on the electric wiring board. What should be noted is that the electric wiring makes the surface of the electric wiring board highly rough. The optical wiring tends to be greatly affected by the surface roughness, with the result that the propagation loss of the optical signal is considered to be increased.
On the other hand, it is desirable for the optical-electrical wiring board, in which an optical wiring is partly substituted for the electrical wiring so as to propagate both the electric signal and the optical signal, to be mounted at a high density or to be miniaturized in view of the object of the use of the optical-electrical wiring board.
An object of the present invention, which has been achieved in view of the situation described above, is to provide an optical-electrical wiring board and a mounted board capable of a high density mounting and miniaturization and permitting propagation of an optical signal with a high efficiency, and a method of manufacturing an optical-electrical wiring board.
According to a first aspect of the present invention, there is provided an optical-electrical wiring board, comprising an electrical wiring board having a through-hole formed therein, and an optical wiring layer laminated on the electrical wiring board and including a core through which the light is propagated and a clad surrounding the core, characterized in that the electrical wiring board includes an electrical wiring formed on a first surface, and mounting means for mounting an optical part, the mounting means being electrically connected to the electric wiring and mounted in the vicinity of the through-hole of the first surface, and the core includes a first waveguide for propagating the light in a first direction along the electrical wiring board and a second waveguide for propagating the light in a second direction perpendicular to the electrical wiring board, the second waveguide crossing the first waveguide and a part of the second waveguide being arranged within the through-hole.
According to a second aspect of the present invention, there is provided an optical-electrical wiring board according to the first aspect of the present invention, characterized in that the optical-electrical wiring board further comprises a mirror arranged in the crossing point between the first waveguide and the second waveguide and serving to reflect the light propagated through one waveguide toward the other waveguide.
According to a third aspect of the present invention, there is provided an optical-electrical wiring board according to the second aspect of the present invention, characterized in that one end of the second waveguide is exposed to the first surface.
According to a fourth aspect of the present invention, there is provided an optical-electrical wiring board according to the second aspect of the present invention, characterized in that the optical-electrical wiring board further comprises a light-collecting lens mounted on the first surface.
According to a fifth aspect of the present invention, there is provided an optical-electrical wiring board according to the second aspect of the present invention, characterized in that the second waveguide is tapered from the first surface toward a second surface opposite to the first surface or from the second surface toward the first surface.
According to a sixth aspect of the present invention, there is provided an optical-electrical wiring board, comprising an electrical wiring board having a through-hole formed therein and an optical wiring layer laminated on the electrical wiring board, characterized in that the electrical wiring board includes an electrical wiring formed on the first surface, and mounting means for mounting an optical part, the mounting means being electrically connected to the electrical wiring and arranged in the vicinity of the through-hole of the first surface, and the optical wiring layer includes a core for propagating the light in a direction extending along the electrical wiring board, and a clad surrounding the core.
According to a seventh aspect of the present invention, there is provided an optical-electrical wiring board according to the sixth aspect of the present invention, characterized in that the optical-electrical wiring board further comprises a mirror for reflecting the light propagated through the core.
According to an eighth aspect of the present invention, there is provided an optical-electrical wiring board according to the first or sixth aspect of the present invention, characterized in that the optical-electrical wiring board further comprises mounting means for mounting an electrical part arranged on the first surface, the mounting means being electrically connected to the electrical wiring.
According to a ninth aspect of the present invention, there is provided an optical-electrical wiring board according to the second or seventh aspect of the present invention, characterized in that the electrical wiring comprises a plurality of layers, and connecting means for electrically connecting the plural layers of the electrical wiring is arranged inside the through-hole.
According to a tenth aspect of the present invention, there is provided an optical-electrical wiring board according to the second or seventh aspect of the present invention, characterized in that the mounting means is arranged such that, when a light-emitting element or a light-receiving element is mounted on the mounting means, the light-emitting surface of the light-emitting element or the light-receiving surface of the light-receiving element is arranged on the axis of the second waveguide.
According to an eleventh aspect of the present invention, there is provided a mounted board prepared by mounting an electric part to the optical-electrical wiring board according to the first or sixth aspect of the present invention.
According to a twelfth aspect of the present invention, there is provided a mounted board prepared by mounting an electric part to the optical-electrical wiring board according to the second or seventh aspect of the present invention.
According to a thirteenth aspect of the present invention, there is provided a method of manufacturing an optical-electrical wiring board, comprising the step of forming a through-hole in an electrical wiring board having an electrical wiring formed on a first surface; the step of bonding an optical wiring layer including a core and a clad surrounding the core to a second surface opposite to the first surface of the electrical wiring board; and the step of forming a mirror in the optical wiring layer, the mirror serving to reflect the light propagated through the core toward the through-hole or to reflect the light passing through the through-hole so as to be incident on the mirror toward the core.
According to a fourteenth aspect of the present invention, there is provided a method of manufacturing an optical-electrical wiring board, comprising the step of forming a first through-hole in an electrical wiring board having an electrical wiring formed on a first surface; the step of filling the first through-hole with a clad; the step of bonding an optical wiring layer including a first core and a clad surrounding the first core to a second surface opposite to the first surface of the electrical wiring board; the step of forming a second through-hole having an inner diameter smaller than the inner diameter of the first through-hole and extending through the electrical wiring board, the first core, and the clad surrounding the first core in a central portion of the first through-hole; the step of filling the second through-hole with a second core so as to form a waveguide extending in a direction perpendicular to the electrical wiring board; and the step of forming a mirror reflecting the light propagated through one core toward the other core in a portion where the first core and the second core are allowed to cross each other.
According to a fifteenth aspect of the present invention, there is provided a method of manufacturing an optical-electrical wiring board, comprising the step of forming a first through-hole in an electrical wiring board having an electrical wiring formed on a first surface; the step of filling the first through-hole with a clad; the step of forming an optical wiring layer including a first core and a clad surrounding the first core on a second surface opposite to the first surface of the electrical wiring board; the step of forming a second through-hole having an inner diameter smaller than the inner diameter of the first through-hole and extending through the electrical wiring board, the first core and the first clad surrounding the first core in a central portion of the first through-hole; the step of filling the second through-hole with a second core so as to form a waveguide extending in a direction perpendicular to the electrical wiring board; and the step of forming a mirror reflecting the light propagated through one core toward the other core in a portion where the first core and the second core are allowed to cross each other.
Further, according to a sixteenth aspect of the present invention, there is provided a method of manufacturing an optical-electrical wiring board according to the fourteenth or fifteenth aspect of the present invention, characterized in that the method further comprises the step of forming a light-collecting lens in one edge of the second core on the side of the first surface.
According to the particular construction defined above, it is possible to realize an optical-electrical wiring board and a mounted board capable of a high density mounting or miniaturization and permitting an optical signal to be propagated at a high efficiency and to realize a method of manufacturing an optical-electrical wiring board.
Various stages of the inventions are included in the embodiments of the present invention, and it is possible to extract various inventions by a suitable combination of a plurality of constituents disclosed herein. For example, where the invention is extracted by omitting several constituents from all the constituents disclosed in the embodiment of the present invention, the omitted portion is supplemented by the known technology in working the extracted invention.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.